The field of the invention is reactive dyes for contact lenses.
The colorants used to manufacture tinted soft contact lenses can often leach out and the lenses lose their original tint when subjected to sterilization conditions or during prolonged storage. There is a need for a suitable tinting agent that can sustain the process requirements of contact lens manufacture. Additionally, the purity levels seen in commercially available colorants are normally very low, the use of which imparts a large amount of undesired salts or impurities to the contact lens formulation. For example, the dye content of a commonly available reactive dye, Reactive Blue 19 (RB19), is below 50% and salts such as sodium sulphate and other organic species make up the rest of the material. The presence of extraneous materials in the dye, in turn, affects the polymerization kinetics and overall yield.
Disclosed herein are methods of making highly pure reactive dyes that can be incorporated into polymerizable compositions without impurities that can negatively impact kinetics and overall polymerization. Background publications include U.S. Pat Nos. 4,468,229, 4,559,059, 5,470,932, 5,944,853, 6,149,692, 7,216,975, and 7,659,325.